Preparation of porous Ti Al-based intermetallics with aligned and elongated pores by freeze-casting was investigated. Engineering Ti-43 Al-9V-1Y powder(D50=50 μm), carboxymethyl cellulose, and guar gum were used to p...Preparation of porous Ti Al-based intermetallics with aligned and elongated pores by freeze-casting was investigated. Engineering Ti-43 Al-9V-1Y powder(D50=50 μm), carboxymethyl cellulose, and guar gum were used to prepare the aqueous-based slurries for freeze-casting. Results showed that the porous Ti Al was obtained by using a freezing temperature of -5 ℃ and the pore structure was tailored by varying the particle content of slurry. The total porosity reduced from 81% to 62% and the aligned pore width dropped from approximately 500 to around 270 μm, with increasing the particle content from 10 to 30 vol.%. Furthermore, the compressive strength along the aligned pores increased from 16 to 120 MPa with the reduction of porosity. The effective thermal conductivities of porous Ti Al were lower than 1.81 W/(m·K) and showed anisotropic property with respect to the pore orientation.展开更多
Bone repair remains an important target in tissue engineering,making the development of bioactive scaffolds for effective bone defect repair a critical objective.In this study,β-tricalcium phosphate(β-TCP)scaffolds ...Bone repair remains an important target in tissue engineering,making the development of bioactive scaffolds for effective bone defect repair a critical objective.In this study,β-tricalcium phosphate(β-TCP)scaffolds incorporated with processed pyritum decoction(PPD)were fabricated using three-dimensional(3D)printing-assisted freeze-casting.The produced composite scaffolds were evaluated for their mechanical strength,physicochemical properties,biocompatibility,in vitro proangiogenic activity,and in vivo efficacy in repairing rabbit femoral defects.They not only demonstrated excellent physicochemical properties,enhanced mechanical strength,and good biosafety but also significantly promoted the proliferation,migration,and aggregation of pro-angiogenic human umbilical vein endothelial cells(HUVECs).In vivo studies revealed that all scaffold groups facilitated osteogenesis at the bone defect site,with theβ-TCP scaffolds loaded with PPD markedly enhancing the expression of neurogenic locus Notch homolog protein 1(Notch1),vascular endothelial growth factor(VEGF),bone morphogenetic protein-2(BMP-2),and osteopontin(OPN).Overall,the scaffolds developed in this study exhibited strong angiogenic and osteogenic capabilities both in vitro and in vivo.The incorporation of PPD notably promoted the angiogenic-osteogenic coupling,thereby accelerating bone repair,which suggests that PPD is a promising material for bone repair and that the PPD/β-TCP scaffolds hold great potential as a bone graft alternative.展开更多
Tendon adhesion,a prevalent complication affecting over 30%of patients after a tendon injury or surgery,results in joint stiffness and impaired mobility.Although current treatments facilitate tendon repair,they are of...Tendon adhesion,a prevalent complication affecting over 30%of patients after a tendon injury or surgery,results in joint stiffness and impaired mobility.Although current treatments facilitate tendon repair,they are often insufficient in preventing adhesions and promoting optimal healing outcomes.To address these challenges,we developed an oriented cryostructured silk fibroin bandage(OCSFB)using the directional freeze-casting methodology.In vitro studies demonstrated that OCSFB provided a favorable microenvironment for cell viability,proliferation,and alignment,concurrently upregulating the expression of tendon-specific genes.In a rat Achilles tendon model,OCSFB significantly reduced adhesion formation and improved tendon healing.RNA-seq analysis further revealed modulation of cell adhesion molecules,substantiating its role in tissue regeneration.The integration of silk fibroin biocompatibility with a unique microstructure that facilitates cellular adhesion and proliferation renders OCSFB a promising approach for mitigating tendon adhesions and improving repair outcomes,establishing it as a robust candidate for clinical application.展开更多
The Al_(2)O_(3)laminated preforms with different layers thickness were prepared by freezing casting in present work.Then,the Al_(2)O_(3p)/AZ91 magnesium matrix laminated materials were obtained by infiltrating the AZ9...The Al_(2)O_(3)laminated preforms with different layers thickness were prepared by freezing casting in present work.Then,the Al_(2)O_(3p)/AZ91 magnesium matrix laminated materials were obtained by infiltrating the AZ91 alloy melt into the Al_(2)O_(3)laminated preform based on pressure infiltration process.Subsequently,the influence of freezing temperature on the microstructure,mechanical properties and fracture behavior of magnesium-based laminates was investigated.The results indicated that with the decrease of freezing temperature,the thickness of Al_(2)O_(3)layers decreases gradually,the number of layers increases obviously,and the interlayers spacing decreases.Accompanied with the decrease of interlayers spacing,the size of Mg17Al12 phase precipitated in the AZ91 alloy layers was refined,and the compression strength and strain were both improved obviously.The micro-cracks initiated in Al_(2)O_(3)layers during loading process,while the AZ91 layers could effectively suppress the initiation and propagation of micro-cracks.Furthermore,the changing layers structure influenced by the decrease of freezing temperature had significant inhibiting effect on the initiation and propagation of micro-cracks,which endowed the Al_(2)O_(3p)/AZ91 magnesium matrix laminated materials with better strength and toughness.Notably,the best compression properties of Al_(2)O_(3p)/AZ91 magnesium matrix laminated materials could be obtained at the freezing temperature of−50℃,the compression strength and elastic modulus of which were the 160%and 250%of monolithic AZ91 alloy,respectively.展开更多
Highly porous Si_(3)N_(4)ceramics with unidirectionally aligned pore channels are gaining significant attention across various fields due to their outstanding functional capabilities.However,achieving high strength in...Highly porous Si_(3)N_(4)ceramics with unidirectionally aligned pore channels are gaining significant attention across various fields due to their outstanding functional capabilities.However,achieving high strength in such unidirectional highly porous Si_(3)N_(4)ceramics remains challenging.Herein,we design and fabricate a novel β-Si_(3)N_(4)scaffold composed of directionally aligned lamellar walls with a textured microstructure by directionally freeze casting ofα-Si_(3)N_(4)suspensions with fine elongatedβ-Si_(3)N_(4)seeds addition,followed by liquid phase sintering.During the sintering,the scaffold exhibited anisotropic shrinkage,and fibrousβ-Si_(3)N_(4)grains were synthesized through epitaxial growth on the seeds preferentially oriented or the nuclei originated fromα-Si_(3)N_(4)powders,resulting in the grains aligned parallel to lamellar walls and bridged the walls.Seed additions of 7 to 15 wt%were beneficial for the optimized distribution of the two types of β-Si_(3)N_(4)grains,which contributed to the excellent resistance to bucking-induced fracture for the walls.Compared with other unidirectional porous Si_(3)N_(4)prepared by freeze-casting in the literature,the Si_(3)N_(4)scaffold exhibited out st anding compressive strength,ranging from 2.8 to 22.0 MPa,as the porosity decreased from 94.4%to 88.0%and the density increased from 175 to 365 mg/cm^(3).The lightweight and strong Si_(3)N_(4)scaffolds are promising candidates for engineering applications in harsh environments.展开更多
Phase change materials(PCMs)can be used for efficient thermal energy harvesting,which has great potential for cost-effective thermal management and energy storage.However,the low intrinsic thermal conductivity of poly...Phase change materials(PCMs)can be used for efficient thermal energy harvesting,which has great potential for cost-effective thermal management and energy storage.However,the low intrinsic thermal conductivity of polymeric PCMs is a bottleneck for fast and efficient heat harvesting.Simultaneously,it is also a challenge to achieve a high thermal conductivity for phase change nanocomposites at low filler loading.Although constructing a three-dimensional(3D)thermally conductive network within PCMs can address these problems,the anisotropy of the 3D framework usually leads to poor thermal conductivity in the direction perpendicular to the alignment of fillers.Inspired by the interlaced structure of spider webs in nature,this study reports a new strategy for fabricating highly thermally conductive phase change composites(sw-GS/PW)with a 3D spider web(sw)-like structured graphene skeleton(GS)by hydrothermal reaction,radial freeze-casting and vacuum impregnation in paraffin wax(PW).The results show that the sw-GS hardly affected the phase transformation behavior of PW at low loading.Especially,sw-GS/PW exhibits both high cross-plane and in-plane thermal conductivity enhancements of~1260%and~840%,respectively,at an ultra-low filler loading of 2.25 vol.%.The thermal infrared results also demonstrate that sw-GS/PW possessed promising applications in battery thermal management.展开更多
With the mandate of worldwide carbon neutralization,pursuing comfortable living environment while consuming less energy is an enticing and unavoidable choice.Novel composite aerogels with super thermal insulation and ...With the mandate of worldwide carbon neutralization,pursuing comfortable living environment while consuming less energy is an enticing and unavoidable choice.Novel composite aerogels with super thermal insulation and high sunlight reflection are developed for energy-efficient buildings.A solvent-assisted freeze-casting strategy is used to produce boron nitride nanosheet/polyvinyl alcohol(BNNS/PVA)composite aerogels with a tailored alignment channel structure.The effects of acetone and BNNS fillers on microstructures and multifunctional properties of aerogels are investigated.The acetone in the PVA suspension enlarges the cell walls to suppress the shrinkage,giving rise to a lower density and a higher porosity,accompanied with much diminished heat conduction throughout the whole product.The addition of BNNS fillers creates whiskers in place of disconnected transverse ligaments between adjacent cell walls,further ameliorating the thermal insulation transverse to the cell wall direction.The resultant BNNS/PVA aerogel delivers an ultralow thermal conductivity of 23.5 mW m^(−1) K^(−1) in the transverse direction.The superinsulating aerogel presents both an infrared stealthy capability and a high solar reflectance of 93.8%over the whole sunlight wave-length,far outperforming commercial expanded polystyrene foams with reflective coatings.The anisotropic BNNS/PVA composite aerogel presents great potential for application in energy-saving buildings.展开更多
Three-dimensional(3D) printing provides a promising way to fabricate biodegradable scaffolds with designer architectures for the regeneration of various tissues.However,the existing3D-printed scaffolds commonly suffer...Three-dimensional(3D) printing provides a promising way to fabricate biodegradable scaffolds with designer architectures for the regeneration of various tissues.However,the existing3D-printed scaffolds commonly suffer from weak cell-scaffold interactions and insufficient cell organizations due to the limited resolution of the 3D-printed features.Here,composite scaffolds with mechanically-robust frameworks and aligned nanofibrous architectures are presented and hybrid manufactured by combining techniques of 3D printing,electrospinning,and unidirectional freeze-casting.It was found that the composite scaffolds provided volume-stable environments and enabled directed cellular infiltration for tissue regeneration.In particular,the nanofibrous architectures with aligned micropores served as artificial extracellular matrix materials and improved the attachment,proliferation,and infiltration of cells.The proposed scaffolds can also support the adipogenic maturation of adipose-derived stem cells(ADSCs)in vitro.Moreover,the composite scaffolds were found to guide directed tissue infiltration and promote nearby neovascularization when implanted into a subcutaneous model of rats,and the addition of ADSCs further enhanced their adipogenic potential.The presented hybrid manufacturing strategy might provide a promising way to produce additional topological cues within 3D-printed scaffolds for better tissue regeneration.展开更多
Lightweight high-strength and tough composites have enormous potentials in a multitude of fields in-cluding biomaterials,sporting goods,aerospace and automobile industries.Herein,we present a strat-egy to develop a no...Lightweight high-strength and tough composites have enormous potentials in a multitude of fields in-cluding biomaterials,sporting goods,aerospace and automobile industries.Herein,we present a strat-egy to develop a novel bulk Al/SiC composite with a nacre/foam hybrid structure to combine excellent lightweight of foams with outstanding strength and toughness of nacre.To reduce the adverse effect of foam pores on mechanical properties,we further propose to strengthen the foams with 3D nanofiber networks,obtaining a nacre/nanofiber reinforced foam structure.Simultaneously,new particle-bubble co-assembly and selective infiltration technologies are proposed to prepare the novel nacre/foam and nacre/nanofiber reinforced foam structures.The nacre/nanofiber reinforced foam composite shows greater specific strength and toughness than the nacre/foam composite,conventional dense Al/SiC composites and many engineering materials.Our approach opens a promising new avenue for the structure design and manufacturing of lightweight,high-performance structural materials.展开更多
A novel antibacterial biomimetic porous titanium implant with good osseointegration was prepared by freeze-casting and thermal oxidation.Bone integration properties of the porous titanium implant were evaluated by cel...A novel antibacterial biomimetic porous titanium implant with good osseointegration was prepared by freeze-casting and thermal oxidation.Bone integration properties of the porous titanium implant were evaluated by cell proliferation assay,alkaline phosphatase activity assay,X-ray examination and hard bone tissue biopsy.The in vitro cell proliferation and the level of differentiation of the group with a modified nano-porous implant surface were significantly higher than those in the group without surface modification and the dense titanium control group(P<0.05).In vivo,bone growth and osteogenesis were found in the experimental groups with modified and unmodified porous titanium implants;osteoblasts in the modified group had more mature differentiation in the pores compared to the unmodified group.Such implants can form solid,biologically compatible bone grafts with bone tissues,exhibiting good osseointegration.展开更多
The porous HA/BaTiO_(3)ceramics have the potential to exhibit superior capabilities to promote bone in-growth.However,there are few reports on in vivo studies.Here,we fabricated bio-inspired porous HA/BaTiO_(3)composi...The porous HA/BaTiO_(3)ceramics have the potential to exhibit superior capabilities to promote bone in-growth.However,there are few reports on in vivo studies.Here,we fabricated bio-inspired porous HA/BaTiO_(3)composites for bone repair via freeze-casting.These composites had a unique microstructure composed of the central canal and radically distributed lamellae,similar to the structure of nature cortical bone unite,the Haversian system.Polarized and non-polarized bio-inspired porous HA/BaTiO_(3)samples were implanted into the femoral condyle of the New Zealand rabbits.It was demonstrated that the polarization of the porous HA/BaTiO_(3)played a favorable part in bone regeneration.Moreover,the combination between the osteoconductivity of the microstructure and augmented osteogenic cell behavior induced by charges on surfaces of polarized porous HA/BaTiO_(3)facilitated bone penetration through the implants.The bio-inspired porous HA/BaTiO_(3)composites are demonstrated to be promising scaffolds for bone repair.展开更多
Porous Si_(3)N_(4)ceramics are promising high-temperature wave transparent materials for use as radomes or antenna windows in hypersonic aircraft.However,a trade-off between the dielectric and thermomechanical propert...Porous Si_(3)N_(4)ceramics are promising high-temperature wave transparent materials for use as radomes or antenna windows in hypersonic aircraft.However,a trade-off between the dielectric and thermomechanical properties is still challenging.Therefore,tailoring the microstructure and properties of porous Si_(3)N_(4)is highly important.In this work,porous Si_(3)N_(4)ceramics with uniform and fine structures were obtained via dual-solvent templating combined with the freeze-casting method.The as-prepared porous Si_(3)N_(4)ceramic,with 56%porosity,possesses high mechanical properties,with flexural strength and compressive strength values of 95±14.8 and 132±4.5 MPa,respectively.The uniform spherical pore structure improved the mechanical properties,and the rod-shaped Si_(3)N_(4)grains facilitated crack deflection.The decreased pore size effectively blocks phonon transport,leading to a low thermal conductivity of only 4.2 W/(K·m).Moreover,the porous Si_(3)N_(4)ceramic maintains a small dielectric constant of 3.3,and the dielectric loss is stable between 1.0×10^(-3)-4.0×10^(-3),which guarantees its potential application in high-temperature wave-transparent components.These results significantly advanced the development of high-performance wave-transparent materials used in hypersonic aircraft.展开更多
Bone,renowned for its elegant hierarchical structure and unique mechanical properties,serves as a constant source of inspiration for the development of synthetic materials.However,achieving accurate replication of bon...Bone,renowned for its elegant hierarchical structure and unique mechanical properties,serves as a constant source of inspiration for the development of synthetic materials.However,achieving accurate replication of bone features in artificial materials with remarkable structural and mechanical similarity remains a significant challenge.In this study,we employed a cascade of continuous fabrication processes,including biomimetic mineralization of collagen,bidirectional freeze-casting,and pressure-driven fusion,to successfully fabricate a macroscopic bulk material known as artificial compact bone(ACB).The ACB material closely replicates the composition,hierarchical structures,and mechanical properties of natural bone.It demonstrates a lamellated alignment of mineralized collagen(MC)microfibrils,similar to those found in natural bone.Moreover,the ACB exhibits a similar high mineral content(70.9%)and density(2.2 g/cm^(3))as natural cortical bone,leading to exceptional mechanical properties such as high stiffness,hardness,and flexural strength that are comparable to those of natural bone.Importantly,the ACB also demonstrates excellent mechanical properties in wet,outstanding biocompatibility,and osteogenic properties in vivo,rendering it suitable for a broad spectrum of biomedical applications,including orthopedic,stomatological,and craniofacial surgeries.展开更多
Bifunctional oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)electrocatalysts with the advantages of excellent activity and stability are the vital components of air cathodes for rechargeable Zn–air b...Bifunctional oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)electrocatalysts with the advantages of excellent activity and stability are the vital components of air cathodes for rechargeable Zn–air batteries(ZABs).Herein,the carbon aerogel with honeycomb-like structure,N and S double doping and loaded with FeCo alloy nanoparticles(NSCA/FeCo)was prepared successfully as cathodes for rechargeable liquid flow and two-dimensional flexible ZABs by clever directional casting.The interaction between the bimetallic alloy and the double-doped carbon with specifical structure,large surface,great conductivity endows NSCA/FeCo with effective ORR/OER active sites and small charge/mass transport barrier,thus achieving outstanding bifunctional catalytic performance.The NSCA/FeCo displays a half-wave potential of+0.85 V(vs.reversible hydrogen electrode(RHE))for ORR and an overpotential of 335 mV at a current density of 10 mA·cm^(−2)for OER,which is even comparable to the performance of noble-metal catalysts in relevant fields(Pt/C for ORR and RuO_(2)for OER).Consequently,the rechargeable liquid flow ZABs assembled with NSCA/FeCo showed excellent performance(maximum power density:132.0 mW·cm^(−2),specific capacity:804.5 Wh·kg^(−1)at 10 mA·cm^(−2),charge and discharge cycle stability of more than 250 cycles).Furthermore,the flexible NSCA/FeCo-based ZABs have a maximum power density of 43.0 mW·cm^(−2),outstanding charging–discharge stability of more than 450 cycles,exhibit good flexibility under different bending conditions.Therefore,this work has provided an efficient bifunctional electrocatalyst for OER/ORR and a promising strategy of air cathodes for rechargeable and wearable ZABs.展开更多
NH_(2)-MIL-125(Ti)is a Ti-MOFs(MOFs:metal-organic frameworks)with high adsorption properties and is therefore widely used for wastewater purification.However,the powdered MOF material suffers from the disadvantages of...NH_(2)-MIL-125(Ti)is a Ti-MOFs(MOFs:metal-organic frameworks)with high adsorption properties and is therefore widely used for wastewater purification.However,the powdered MOF material suffers from the disadvantages of being difficult to separate and being potentially wasted due to easy agglomeration,which limits its application in practical applications.Here,a mesoporous Ti-MOF/polymer(PEG,PVA,and PAM)monolithic material was prepared by freeze casting in liquid nitrogen(-196℃)as an adsorbent for wastewater remediation.The composites could be easily picked up with tweezers and used for recovery tests.Characterization results such as XRD,BET,FT-IR,and SEM proved the successful synthesis of Ti-MOF/polymer.Adsorption tests using 100 mg/L methylene blue(MB)simulated wastewater showed that the Ti-MOF/PEG monolithic material had the best adsorption capacity.The order of adsorption was Ti-MOF@PEG10(747.4 mg/g)>Ti-MOF@PVA10(687.4 mg/g)>Ti-MOF@PAM10(633.7 mg/g)>NH_(2)-MIL-125(Ti)(571.4 mg/g).The effects of polymer dosage,different pollutants(methylene blue,methyl orange,indigo,actual textile wastewater),pH,anions,and cations on the adsorption effect of Ti-MOF/polymer were also investigated.It was demonstrated that all the above pollutants were well adsorbed by this Ti-MOF/polymer in the pH range 3-9.The adsorption isotherms and kinetic data are fully consistent with the Langmuir and pseudo-secondary models.This suggests that the adsorption between the pollutant and the adsorbent is a chemical interaction.Thermodynamic studies indicate that the adsorption process is exothermic and spontaneous.This work provides the potential methods to fabricate Ti-MOF/polymer monolith to avoid the pollution from powdery adsorbents that could be practical applications.展开更多
基金Projects(51775418,51375372)supported by the National Natural Science Foundation of China
文摘Preparation of porous Ti Al-based intermetallics with aligned and elongated pores by freeze-casting was investigated. Engineering Ti-43 Al-9V-1Y powder(D50=50 μm), carboxymethyl cellulose, and guar gum were used to prepare the aqueous-based slurries for freeze-casting. Results showed that the porous Ti Al was obtained by using a freezing temperature of -5 ℃ and the pore structure was tailored by varying the particle content of slurry. The total porosity reduced from 81% to 62% and the aligned pore width dropped from approximately 500 to around 270 μm, with increasing the particle content from 10 to 30 vol.%. Furthermore, the compressive strength along the aligned pores increased from 16 to 120 MPa with the reduction of porosity. The effective thermal conductivities of porous Ti Al were lower than 1.81 W/(m·K) and showed anisotropic property with respect to the pore orientation.
基金supported by the National Science Foundation of China(Nos.81373970,81773902,81973484,and 32171402)the National College Students Innovation and Entrepreneurship Training Program(No.201810315019)+4 种基金the Postgraduate Research and Practice Innovation Program of Jiangsu Province(Nos.SJCX21_0712 and KYCX23_2052)the Scientific Research Project of Jiangsu Provincial Association of Traditional Chinese Medicine(No.XYLD2024013)the Youth Scientific Research Project of Jiangyin Municipal Health Commission(No.Q202402)the Natural Science Foundation Project of Nanjing University of Chinese Medicine(No.XZR2024173)the Jiangyin Science and Technology Innovation Special Fund Project(No.JY0603A011014230032PB),China.
文摘Bone repair remains an important target in tissue engineering,making the development of bioactive scaffolds for effective bone defect repair a critical objective.In this study,β-tricalcium phosphate(β-TCP)scaffolds incorporated with processed pyritum decoction(PPD)were fabricated using three-dimensional(3D)printing-assisted freeze-casting.The produced composite scaffolds were evaluated for their mechanical strength,physicochemical properties,biocompatibility,in vitro proangiogenic activity,and in vivo efficacy in repairing rabbit femoral defects.They not only demonstrated excellent physicochemical properties,enhanced mechanical strength,and good biosafety but also significantly promoted the proliferation,migration,and aggregation of pro-angiogenic human umbilical vein endothelial cells(HUVECs).In vivo studies revealed that all scaffold groups facilitated osteogenesis at the bone defect site,with theβ-TCP scaffolds loaded with PPD markedly enhancing the expression of neurogenic locus Notch homolog protein 1(Notch1),vascular endothelial growth factor(VEGF),bone morphogenetic protein-2(BMP-2),and osteopontin(OPN).Overall,the scaffolds developed in this study exhibited strong angiogenic and osteogenic capabilities both in vitro and in vivo.The incorporation of PPD notably promoted the angiogenic-osteogenic coupling,thereby accelerating bone repair,which suggests that PPD is a promising material for bone repair and that the PPD/β-TCP scaffolds hold great potential as a bone graft alternative.
基金sponsored by the National Natural Science Foundation of China(Nos.52235007,T2121004,and 52325504)the Key R&D Program of Zhejiang(No.2024SSYS0027)+1 种基金the National Key Research and Development Program of China(Nos.2024YFB4607700 and 2024YFB4607703)the China National Postdoctoral Program for Innovative Talents(No.BX20240312)。
文摘Tendon adhesion,a prevalent complication affecting over 30%of patients after a tendon injury or surgery,results in joint stiffness and impaired mobility.Although current treatments facilitate tendon repair,they are often insufficient in preventing adhesions and promoting optimal healing outcomes.To address these challenges,we developed an oriented cryostructured silk fibroin bandage(OCSFB)using the directional freeze-casting methodology.In vitro studies demonstrated that OCSFB provided a favorable microenvironment for cell viability,proliferation,and alignment,concurrently upregulating the expression of tendon-specific genes.In a rat Achilles tendon model,OCSFB significantly reduced adhesion formation and improved tendon healing.RNA-seq analysis further revealed modulation of cell adhesion molecules,substantiating its role in tissue regeneration.The integration of silk fibroin biocompatibility with a unique microstructure that facilitates cellular adhesion and proliferation renders OCSFB a promising approach for mitigating tendon adhesions and improving repair outcomes,establishing it as a robust candidate for clinical application.
基金supported by the National Key Research and Development Program for Young Scientists(Grant No.2021YFB3703300)the National Natural Science Foundation of China(Grant Nos.52271109 and 52001223)+1 种基金the Major Special Plan for Science and Technology in Shanxi Province(Grant No.202201050201012)the Special Fund Project for Guiding Local Science and Technology Development by the Central Government(Grant No.YDZJSX2021B019)。
文摘The Al_(2)O_(3)laminated preforms with different layers thickness were prepared by freezing casting in present work.Then,the Al_(2)O_(3p)/AZ91 magnesium matrix laminated materials were obtained by infiltrating the AZ91 alloy melt into the Al_(2)O_(3)laminated preform based on pressure infiltration process.Subsequently,the influence of freezing temperature on the microstructure,mechanical properties and fracture behavior of magnesium-based laminates was investigated.The results indicated that with the decrease of freezing temperature,the thickness of Al_(2)O_(3)layers decreases gradually,the number of layers increases obviously,and the interlayers spacing decreases.Accompanied with the decrease of interlayers spacing,the size of Mg17Al12 phase precipitated in the AZ91 alloy layers was refined,and the compression strength and strain were both improved obviously.The micro-cracks initiated in Al_(2)O_(3)layers during loading process,while the AZ91 layers could effectively suppress the initiation and propagation of micro-cracks.Furthermore,the changing layers structure influenced by the decrease of freezing temperature had significant inhibiting effect on the initiation and propagation of micro-cracks,which endowed the Al_(2)O_(3p)/AZ91 magnesium matrix laminated materials with better strength and toughness.Notably,the best compression properties of Al_(2)O_(3p)/AZ91 magnesium matrix laminated materials could be obtained at the freezing temperature of−50℃,the compression strength and elastic modulus of which were the 160%and 250%of monolithic AZ91 alloy,respectively.
基金supported by the National Natural Science Foundation of China(Nos.U2066216 and 52372068)the Na-tional Key R&D Program of China(Nos.2017YFB0310300 and 2017YFB0903800)the China Postdoctoral Science Foundation(No.2020M672248).
文摘Highly porous Si_(3)N_(4)ceramics with unidirectionally aligned pore channels are gaining significant attention across various fields due to their outstanding functional capabilities.However,achieving high strength in such unidirectional highly porous Si_(3)N_(4)ceramics remains challenging.Herein,we design and fabricate a novel β-Si_(3)N_(4)scaffold composed of directionally aligned lamellar walls with a textured microstructure by directionally freeze casting ofα-Si_(3)N_(4)suspensions with fine elongatedβ-Si_(3)N_(4)seeds addition,followed by liquid phase sintering.During the sintering,the scaffold exhibited anisotropic shrinkage,and fibrousβ-Si_(3)N_(4)grains were synthesized through epitaxial growth on the seeds preferentially oriented or the nuclei originated fromα-Si_(3)N_(4)powders,resulting in the grains aligned parallel to lamellar walls and bridged the walls.Seed additions of 7 to 15 wt%were beneficial for the optimized distribution of the two types of β-Si_(3)N_(4)grains,which contributed to the excellent resistance to bucking-induced fracture for the walls.Compared with other unidirectional porous Si_(3)N_(4)prepared by freeze-casting in the literature,the Si_(3)N_(4)scaffold exhibited out st anding compressive strength,ranging from 2.8 to 22.0 MPa,as the porosity decreased from 94.4%to 88.0%and the density increased from 175 to 365 mg/cm^(3).The lightweight and strong Si_(3)N_(4)scaffolds are promising candidates for engineering applications in harsh environments.
基金This work was supported by the National Natural Science Foundation of China(Numbers:U19A20105,51877132).
文摘Phase change materials(PCMs)can be used for efficient thermal energy harvesting,which has great potential for cost-effective thermal management and energy storage.However,the low intrinsic thermal conductivity of polymeric PCMs is a bottleneck for fast and efficient heat harvesting.Simultaneously,it is also a challenge to achieve a high thermal conductivity for phase change nanocomposites at low filler loading.Although constructing a three-dimensional(3D)thermally conductive network within PCMs can address these problems,the anisotropy of the 3D framework usually leads to poor thermal conductivity in the direction perpendicular to the alignment of fillers.Inspired by the interlaced structure of spider webs in nature,this study reports a new strategy for fabricating highly thermally conductive phase change composites(sw-GS/PW)with a 3D spider web(sw)-like structured graphene skeleton(GS)by hydrothermal reaction,radial freeze-casting and vacuum impregnation in paraffin wax(PW).The results show that the sw-GS hardly affected the phase transformation behavior of PW at low loading.Especially,sw-GS/PW exhibits both high cross-plane and in-plane thermal conductivity enhancements of~1260%and~840%,respectively,at an ultra-low filler loading of 2.25 vol.%.The thermal infrared results also demonstrate that sw-GS/PW possessed promising applications in battery thermal management.
基金supported by the Research Grants Council(GRF Projects:16205517,16209917,and 16200720)and Innovation and Technology Commission(ITS/012/19)of Hong Kong SAR.Technical assistance from the Materials Characterization and Preparation Facility(MCPF)the Advanced Engineering Material Facility(AEMF)the Environmental Central Facility(ENVF)at HKUST are also appreciated.
文摘With the mandate of worldwide carbon neutralization,pursuing comfortable living environment while consuming less energy is an enticing and unavoidable choice.Novel composite aerogels with super thermal insulation and high sunlight reflection are developed for energy-efficient buildings.A solvent-assisted freeze-casting strategy is used to produce boron nitride nanosheet/polyvinyl alcohol(BNNS/PVA)composite aerogels with a tailored alignment channel structure.The effects of acetone and BNNS fillers on microstructures and multifunctional properties of aerogels are investigated.The acetone in the PVA suspension enlarges the cell walls to suppress the shrinkage,giving rise to a lower density and a higher porosity,accompanied with much diminished heat conduction throughout the whole product.The addition of BNNS fillers creates whiskers in place of disconnected transverse ligaments between adjacent cell walls,further ameliorating the thermal insulation transverse to the cell wall direction.The resultant BNNS/PVA aerogel delivers an ultralow thermal conductivity of 23.5 mW m^(−1) K^(−1) in the transverse direction.The superinsulating aerogel presents both an infrared stealthy capability and a high solar reflectance of 93.8%over the whole sunlight wave-length,far outperforming commercial expanded polystyrene foams with reflective coatings.The anisotropic BNNS/PVA composite aerogel presents great potential for application in energy-saving buildings.
基金financially supported by the National Key Research and Development Program of China(2018YFA0703003)the National Natural Science Foundation of China (52125501)+2 种基金the Key Research Project of Shaanxi Province (2021LLRH-08,2021GXLH-Z-028)the Program for Innovation Team of Shaanxi Province (2023-CX-TD-17)the Fundamental Research Funds for the Central Universities。
文摘Three-dimensional(3D) printing provides a promising way to fabricate biodegradable scaffolds with designer architectures for the regeneration of various tissues.However,the existing3D-printed scaffolds commonly suffer from weak cell-scaffold interactions and insufficient cell organizations due to the limited resolution of the 3D-printed features.Here,composite scaffolds with mechanically-robust frameworks and aligned nanofibrous architectures are presented and hybrid manufactured by combining techniques of 3D printing,electrospinning,and unidirectional freeze-casting.It was found that the composite scaffolds provided volume-stable environments and enabled directed cellular infiltration for tissue regeneration.In particular,the nanofibrous architectures with aligned micropores served as artificial extracellular matrix materials and improved the attachment,proliferation,and infiltration of cells.The proposed scaffolds can also support the adipogenic maturation of adipose-derived stem cells(ADSCs)in vitro.Moreover,the composite scaffolds were found to guide directed tissue infiltration and promote nearby neovascularization when implanted into a subcutaneous model of rats,and the addition of ADSCs further enhanced their adipogenic potential.The presented hybrid manufacturing strategy might provide a promising way to produce additional topological cues within 3D-printed scaffolds for better tissue regeneration.
基金financially supported by the National Key R&D Program of China(No.2018YFA0702800)the National Natural Sci-ence Foundation of China(No.51002019)the Fundamental Re-search Funds for the Central Universities(Nos.DUT21GF309 and DUT22LAB114).
文摘Lightweight high-strength and tough composites have enormous potentials in a multitude of fields in-cluding biomaterials,sporting goods,aerospace and automobile industries.Herein,we present a strat-egy to develop a novel bulk Al/SiC composite with a nacre/foam hybrid structure to combine excellent lightweight of foams with outstanding strength and toughness of nacre.To reduce the adverse effect of foam pores on mechanical properties,we further propose to strengthen the foams with 3D nanofiber networks,obtaining a nacre/nanofiber reinforced foam structure.Simultaneously,new particle-bubble co-assembly and selective infiltration technologies are proposed to prepare the novel nacre/foam and nacre/nanofiber reinforced foam structures.The nacre/nanofiber reinforced foam composite shows greater specific strength and toughness than the nacre/foam composite,conventional dense Al/SiC composites and many engineering materials.Our approach opens a promising new avenue for the structure design and manufacturing of lightweight,high-performance structural materials.
基金Projects (51290295,51305464) supported by the National Natural Science Foundation of ChinaProject (2016JJ6156) supported by the Natural Science Foundation of Hunan Province,China+1 种基金Project (2016JC2064) supported by Key Research and Development Project of Hunan Province,ChinaProject (20130162120094) supported by Specialized Research Fund for the Doctoral Program of Higher Education,China
文摘A novel antibacterial biomimetic porous titanium implant with good osseointegration was prepared by freeze-casting and thermal oxidation.Bone integration properties of the porous titanium implant were evaluated by cell proliferation assay,alkaline phosphatase activity assay,X-ray examination and hard bone tissue biopsy.The in vitro cell proliferation and the level of differentiation of the group with a modified nano-porous implant surface were significantly higher than those in the group without surface modification and the dense titanium control group(P<0.05).In vivo,bone growth and osteogenesis were found in the experimental groups with modified and unmodified porous titanium implants;osteoblasts in the modified group had more mature differentiation in the pores compared to the unmodified group.Such implants can form solid,biologically compatible bone grafts with bone tissues,exhibiting good osseointegration.
基金This study was financially supported by the National Natural Science Foundation of China(Nos.81571021 and 51072235).
文摘The porous HA/BaTiO_(3)ceramics have the potential to exhibit superior capabilities to promote bone in-growth.However,there are few reports on in vivo studies.Here,we fabricated bio-inspired porous HA/BaTiO_(3)composites for bone repair via freeze-casting.These composites had a unique microstructure composed of the central canal and radically distributed lamellae,similar to the structure of nature cortical bone unite,the Haversian system.Polarized and non-polarized bio-inspired porous HA/BaTiO_(3)samples were implanted into the femoral condyle of the New Zealand rabbits.It was demonstrated that the polarization of the porous HA/BaTiO_(3)played a favorable part in bone regeneration.Moreover,the combination between the osteoconductivity of the microstructure and augmented osteogenic cell behavior induced by charges on surfaces of polarized porous HA/BaTiO_(3)facilitated bone penetration through the implants.The bio-inspired porous HA/BaTiO_(3)composites are demonstrated to be promising scaffolds for bone repair.
基金supported by the National Natural Science Foundation of China(Grant No.52202078)the Leading Talent Project of the National Special Support Program(Grant No.2022WRLJ003)+1 种基金the Guangdong Basic and Applied Basic Research Foundation for Distinguished Young Scholars(Grant No.2021B1515020083)the Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2021A1515110293 and 2022A1515012201).
文摘Porous Si_(3)N_(4)ceramics are promising high-temperature wave transparent materials for use as radomes or antenna windows in hypersonic aircraft.However,a trade-off between the dielectric and thermomechanical properties is still challenging.Therefore,tailoring the microstructure and properties of porous Si_(3)N_(4)is highly important.In this work,porous Si_(3)N_(4)ceramics with uniform and fine structures were obtained via dual-solvent templating combined with the freeze-casting method.The as-prepared porous Si_(3)N_(4)ceramic,with 56%porosity,possesses high mechanical properties,with flexural strength and compressive strength values of 95±14.8 and 132±4.5 MPa,respectively.The uniform spherical pore structure improved the mechanical properties,and the rod-shaped Si_(3)N_(4)grains facilitated crack deflection.The decreased pore size effectively blocks phonon transport,leading to a low thermal conductivity of only 4.2 W/(K·m).Moreover,the porous Si_(3)N_(4)ceramic maintains a small dielectric constant of 3.3,and the dielectric loss is stable between 1.0×10^(-3)-4.0×10^(-3),which guarantees its potential application in high-temperature wave-transparent components.These results significantly advanced the development of high-performance wave-transparent materials used in hypersonic aircraft.
基金supported by the National Key R&D Program of China(No.2023YFC2412300 and 2020YFC1107600)the Key R&D Program in Shandong Province(No.2019JZZY011106)the Foshan-Tsinghua Industry-University-Research Cooperation Collaborative Innovation Project.
文摘Bone,renowned for its elegant hierarchical structure and unique mechanical properties,serves as a constant source of inspiration for the development of synthetic materials.However,achieving accurate replication of bone features in artificial materials with remarkable structural and mechanical similarity remains a significant challenge.In this study,we employed a cascade of continuous fabrication processes,including biomimetic mineralization of collagen,bidirectional freeze-casting,and pressure-driven fusion,to successfully fabricate a macroscopic bulk material known as artificial compact bone(ACB).The ACB material closely replicates the composition,hierarchical structures,and mechanical properties of natural bone.It demonstrates a lamellated alignment of mineralized collagen(MC)microfibrils,similar to those found in natural bone.Moreover,the ACB exhibits a similar high mineral content(70.9%)and density(2.2 g/cm^(3))as natural cortical bone,leading to exceptional mechanical properties such as high stiffness,hardness,and flexural strength that are comparable to those of natural bone.Importantly,the ACB also demonstrates excellent mechanical properties in wet,outstanding biocompatibility,and osteogenic properties in vivo,rendering it suitable for a broad spectrum of biomedical applications,including orthopedic,stomatological,and craniofacial surgeries.
基金the Fundamental Research Funds for the Central Universities(No.30920041108).
文摘Bifunctional oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)electrocatalysts with the advantages of excellent activity and stability are the vital components of air cathodes for rechargeable Zn–air batteries(ZABs).Herein,the carbon aerogel with honeycomb-like structure,N and S double doping and loaded with FeCo alloy nanoparticles(NSCA/FeCo)was prepared successfully as cathodes for rechargeable liquid flow and two-dimensional flexible ZABs by clever directional casting.The interaction between the bimetallic alloy and the double-doped carbon with specifical structure,large surface,great conductivity endows NSCA/FeCo with effective ORR/OER active sites and small charge/mass transport barrier,thus achieving outstanding bifunctional catalytic performance.The NSCA/FeCo displays a half-wave potential of+0.85 V(vs.reversible hydrogen electrode(RHE))for ORR and an overpotential of 335 mV at a current density of 10 mA·cm^(−2)for OER,which is even comparable to the performance of noble-metal catalysts in relevant fields(Pt/C for ORR and RuO_(2)for OER).Consequently,the rechargeable liquid flow ZABs assembled with NSCA/FeCo showed excellent performance(maximum power density:132.0 mW·cm^(−2),specific capacity:804.5 Wh·kg^(−1)at 10 mA·cm^(−2),charge and discharge cycle stability of more than 250 cycles).Furthermore,the flexible NSCA/FeCo-based ZABs have a maximum power density of 43.0 mW·cm^(−2),outstanding charging–discharge stability of more than 450 cycles,exhibit good flexibility under different bending conditions.Therefore,this work has provided an efficient bifunctional electrocatalyst for OER/ORR and a promising strategy of air cathodes for rechargeable and wearable ZABs.
基金the National Natural Science Foundation of China(No.21902118)
文摘NH_(2)-MIL-125(Ti)is a Ti-MOFs(MOFs:metal-organic frameworks)with high adsorption properties and is therefore widely used for wastewater purification.However,the powdered MOF material suffers from the disadvantages of being difficult to separate and being potentially wasted due to easy agglomeration,which limits its application in practical applications.Here,a mesoporous Ti-MOF/polymer(PEG,PVA,and PAM)monolithic material was prepared by freeze casting in liquid nitrogen(-196℃)as an adsorbent for wastewater remediation.The composites could be easily picked up with tweezers and used for recovery tests.Characterization results such as XRD,BET,FT-IR,and SEM proved the successful synthesis of Ti-MOF/polymer.Adsorption tests using 100 mg/L methylene blue(MB)simulated wastewater showed that the Ti-MOF/PEG monolithic material had the best adsorption capacity.The order of adsorption was Ti-MOF@PEG10(747.4 mg/g)>Ti-MOF@PVA10(687.4 mg/g)>Ti-MOF@PAM10(633.7 mg/g)>NH_(2)-MIL-125(Ti)(571.4 mg/g).The effects of polymer dosage,different pollutants(methylene blue,methyl orange,indigo,actual textile wastewater),pH,anions,and cations on the adsorption effect of Ti-MOF/polymer were also investigated.It was demonstrated that all the above pollutants were well adsorbed by this Ti-MOF/polymer in the pH range 3-9.The adsorption isotherms and kinetic data are fully consistent with the Langmuir and pseudo-secondary models.This suggests that the adsorption between the pollutant and the adsorbent is a chemical interaction.Thermodynamic studies indicate that the adsorption process is exothermic and spontaneous.This work provides the potential methods to fabricate Ti-MOF/polymer monolith to avoid the pollution from powdery adsorbents that could be practical applications.
